The development of a novel treatment of head and neck tumors based on fast neuron brachytherapy, with or without dose augmentation by neutron by neutron capture in boron, it is proposed. Use of brachytherapy approach rather than external beam irradiation will allow intracavity delivery of neutrons leading to vastly improved tumor to healthy tissue dose ratios. Significant healthy tissue sparing should allow the delivery of larger tumor doses than those delivered using external beams, and larger tumor doses would, in turn, lead to improved local control. Unlike the case with many cancer types in which patients die of distant metastases, patients with head and neck tumors tend to die of local and regional involvement. Thus, improving local control is expected to lead to improved patient survival. Accelerator-based neutron brachytherapy would involve the insertion into a patient cavity or tumor of a long, narrow accelerator tube having a neutron-producing target at the tip. In Phase I, a computational model of neutron transport in the human head and neck will be developed and used to determine the most effective neutron source parameters for irradiation of head and neck tumors. The dose characteristics of fast neutron brachytherapy will be evaluated relative to external beam fast neutron therapy, and the potential tumor dose enhancement provided by boron neutron capture will be quantified. Finally, the engineering requirements for a clinically useful accelerator-based neutron brachytherapy source will be determine. PROPOSED COMMERCIAL APPLICATIONS: If neutron brachytherapy is found to provide significant advantages for the treatment of head and neck tumors, then a market will exist for brachytherapy systems. Head and neck cancers account for 5-6% of all cancers in the U.S., and as high as 50% of cancers in developing countries. Neutron brachytherapy may also prove useful in the treatment of other prevalent cancers, such as prostate cancer. An accelerator-based brachytherapy system could be made compact enough to be installed and operated at major medical centers.